Absorbent Article with a Slitted Absorbent Core

ABSTRACT

The invention relates to slit absorbent articles and the use of slits in absorbent materials to provide improved liquid intake rate, flexibility and softness compared to the unmodified material. The absorbent material, including superabsorbent materials, are particularly useful as absorbent cores in disposable absorbent articles such as diapers, incontinent products, sanitary napkins and the like.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation application of U.S. application Ser.No. 14/336,864 filed on Jul. 21, 2014 (pending), which is a Divisionalof U.S. patent application Ser. No. 12/138,112, filed Jun. 12, 2008 (nowU.S. Pat. No. 8,785,715 B2, issued on Jul. 22, 2014), which claimspriority under 35 U.S.C. 119(e) from provisional U.S. Patent ApplicationNo. 60/943,321 filed Jun. 12, 2007 (now expired) (which is herebyincorporated by reference for all purposes and made a part of thepresent disclosure).

TECHNICAL FIELD

The present invention relates to liquid absorbing articles incorporatingsuperabsorbents and, more particularly, to the use of slits in theabsorbent core to provide the requisite properties of fast fluid intake,thinness, flexibility and softness.

BACKGROUND OF THE INVENTION

Absorbent articles such as disposable diapers, adult incontinent pads,sanitary napkins and the like are generally provided with an absorbentcore material to receive and retain body liquids. Typical compositionsof absorbent core materials are particulate, absorbent, polymericcompositions, often referred to as “hydrogels” or “superabsorbents”,which are capable of absorbing large quantities of liquids such as waterand body exudates. Fibrous components such as pulp or other syntheticfibers are incorporated into the composite together with thesuperabsorbent to provide acceptable fluid handling characteristics offast liquid intake, liquid capture and reduced “gel blocking”. Gelblocking is a phenomenon that occurs when the swelling of the absorbentparticles as a result of liquid absorption increases the resistance toliquid flow within the material. It is generally believed that thefibrous component provides stable interparticle liquid channels thatminimize the gel blocking effect.

For fit, comfort and aesthetic reasons, it is highly desired to makedisposable absorbent articles as thin as possible. Disposable absorbentarticles can be reduced in thickness by reducing the absorbent corethickness. Thinner diapers are less bulky to wear, fit better andprovide more comfort to the wearer. To achieve the lowest absorbent corethickness for a given level of absorbent capacity, the superabsorbentcontent is preferably increased toward 100%, that is, the fibercomponent of the absorbent core is reduced to near zero percent. Thecomposite of superabsorbent content and fiber component oftentimes isalso subjected to densification to achieve and maintain reducedthickness. However, such absorbent composites generally display muchslower liquid intake characteristics due to their high compositedensity, high gel blocking characteristics, low permeability to liquidpassage that that cause liquid leakage. In addition, higher stiffnessand rigidity of such structures lead to absorbent products with poor fitand comfort.

As disclosed in prior art, the slower liquid intake ofsuperabsorbent-containing absorbent cores can be compensated for byadding liquid-holding layers of materials on top of the absorbent core.These are usually fibrous or film structures capable of accepting theliquid insult at its rate of delivery and temporarily holding the liquiduntil the absorbent core can fully absorb and retain the insult. Theseelements are termed surge or acquisition layers, as shown in U.S. Pat.No. 5,364,382. However, increasing the number of surge layers tocompensate for a much slower absorbing core adds to the thickness andcost of the absorbent article.

Other approaches such as discontinuous and patterned placement of thesuperabsorbent material or composite have been disclosed in the art,such as U.S. Pat. Nos. 4,560,372 and 5,868,724. Voids are created in theabsorbent composite, hence the surface coverage of the absorbentcomposite is less than 100%. Implementation of approaches is relativelycomplex. Furthermore the full area available for absorbency is notutilized, and consequently the article is thicker than one with arelatively uniform distribution of superabsorbent material.

Hence, there remains a need for an absorbent core that is thin, havinghigh absorbent capacity with good fluid intake rate characteristics,soft, and flexible that can be used in absorbent articles such asdisposable diapers, adult incontinent pads or briefs, sanitary napkinsand the like.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to the use of one or more slits withinan absorbent composite of a disposable absorbent article. The one ormore slits provide for high performance disposable absorbent articleswhich are thin, soft and flexible. Such an absorbent composite may beemployed as the primary component of the absorbent core, together with atopsheet, a backsheet, containment walls or cuffs, and other elements(e.g., an acquisition layer) of the disposable absorbent article. Amongthe characteristics which may be exhibited by embodiments of theinventive absorbent article are improved fit and appearance, improvedabsorption and liquid containment properties, simpler, more efficientmanufacturing process, and a thinner, more compact construction.

It is therefore an object of the invention to provide a disposableabsorbent article having improved overall thinness, improved rate ofliquid acquisition, and with an absorbent core which is soft andflexible.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages of the invention will be describedhereinafter which form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand specific embodiment disclosed may be readily utilized as a basis formodifying or designing other structures for carrying out the samepurposes of the present invention. It should also be realized by thoseskilled in the art that such equivalent constructions do not depart fromthe spirit and scope of the invention as set forth in the appendedclaims. The novel features which are believed to be characteristic ofthe invention, both as to its organization and method of operation,together with further objects and advantages will be better understoodfrom the following description when considered in connection with theaccompanying figures. It is to be expressly understood, however, thateach of the figures is provided for the purpose of illustration anddescription only and is not intended as a definition of the limits ofthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, reference isnow made to the following descriptions taken in conjunction with theaccompanying drawing, in which:

FIG. 1 is a vertical cross-section illustration of the absorbentcomposite used as absorbent core;

FIG. 2A is a top plan view of an absorbent core with a multiplicity ofslits arranged in various patterns along the machine direction (MD) andcross direction (CD) wherein the slit is a partial slit traversing aportion of the full absorbent core thickness;

FIG. 2B is a top plan view of an absorbent core with a multiplicity ofslits arranged in various patterns along the machine direction (MD) andcross direction (CD) wherein the slit is a through slit traversing thefull absorbent core thickness;

FIG. 3 is a top plan view of an arrangement of an embodiment of thepresent invention having an absorbent core with long side slits toachieve side bending;

FIG. 4 is a top plan view of an absorbent core with center and sideslits and a multiplicity of smaller slits placed between the long slits;

FIG. 5 is a top plan view of an absorbent core with patterned slits atends and sides in addition to long side slits;

FIG. 6 is a cross sectional view along the transverse direction of alayered absorbent composite showing a slit absorbent core as a top layerover an unslit absorbent core as a lower layer;

FIG. 7 is a cross sectional view along the longitudinal direction of alayered absorbent composite showing a slit absorbent core as an upperlayer positioned around the liquid target region and an unslit absorbentcore as lower layer absorbent composite; and

FIG. 8 depicts a top plan view and a perspective view of appropriatelyplaced slits in the absorbent composite that provide bend areas andenable the absorbent article to follow the body curvature; and

FIGS. 9 and 10 are top plan views of shaped absorbents derived from arectangular absorbent core through slitting and folding.

DETAILED DESCRIPTION OF THE INVENTION

It has been discovered that the addition of an adequate level ofslitting to a absorbent composite causes a significant improvement inits liquid intake and a corresponding increase in softness andflexibility without an increase in composite thickness and without areduction of machine direction (MD) strength. Machine direction strengthis particularly advantageous to the manufacturing and processing of theabsorbent articles.

For purposes of increasing liquid intake, the appropriate level ofslitting should be greater than 0.1. By definition, a material that doesnot contain any slits has a “slit level” of zero. The level of slittingcan be determined by summing the total slit perimeter formed from themultiplicity of slits used and normalizing the total slit perimeter tothe planar area of the composite encompassing the slit region. Forexample, 5 slits that are 1 cm in length distributed in a 5 cm×10 cmarea of the absorbent would yield a slit level of 0.2 cm⁻. In thisexample, the total slit perimeter is 1 cm×2×5=10 cm; planar area is 5cm×10 cm=50 cm²; and slit level is 10 cm/50 cm²=0.2 cm⁻¹. For purposesof increasing softness and flexibility, the slit size and placement canbe distributed according to a pattern that yields the appropriateimprovement. In general, a higher slit level leads to both faster intakeand higher softness and flexibility.

As used herein, the term “slit” is defined as a narrow cut, opening oraperture. The slit may be straight or curved and may be disposed in anyplanar orientation within the absorbent composite, including vertical orangled relative to the top surface. The slit depth may vary betweenslits and may also vary along a slit length. The slit depth can be equalto the thickness of the absorbent core. Such slits can be referred to as“partial slits”, such as shown in FIG. 2A or as “through slits”, such asshown in FIG. 2B. During manufacturing of the absorbent article, theslitting of the absorbent core may take place before or after theabsorbent core is connected to a back sheet.

Without being bound by theory, it is believed that the slit regions havehigher liquid intake rate compared to the non-slit areas due to anincrease in liquid permeability and an increase in surface area aroundthe slit. Similarly, slits provide a material discontinuity and a regionof zero or very low modulus that facilitates the bending or folding ofthe absorbent core along the slit region also resulting in amacroscopically flexible material. It is also possible that the slitsfacilitate capillary flow of liquid toward an interior of the absorbentcore. Slit widths, defined as the distance between walls of a slit, mayrange from about 1 micron to about 1000 microns.

Appropriately placed slits in the absorbent core provide bend and foldlines that can be utilized in creating shaped absorbent cores fromrectangular absorbent composites resulting in simpler and more efficientmanufacturing processes. For example, in a diaper, long slits placedalong the crotch area and towards the side edges of the absorbent coreenables the folding inward of these outboard edges creating an“hourglass” shaped absorbent core that can provide enhanced fit.Moreover, because of such folding, more absorbent composite is added tothe target area, and a bumper-like absorbent structure is created thatcan reduce leakage in the crotch area.

Other areas in the absorbent core can be selectively slit to provide thedesired bending characteristics that enable the absorbent article tofollow the body curvature for improved fit and appearance.

Slitting may be accomplished through shear, score or burst slitting suchas provided by rotating or stationary knives, cutting dies, laser orwater jet cutting. The absorbent material may also be subjected tomechanical softening prior to the addition of slits. Examples of suchsoftening processes are creping, groove or ring-rolling, and embossing.

FIG. 1 depicts a magnified illustration of an absorbent composite orcore 100 used in an embodiment of the present invention. Core 100 maydefine one or more layers within an absorbent core of a disposableabsorbent article 8, as shown in FIG. 2A. Core 100 includessuperabsorbent particles 102 which are covered or intermixed withextremely fine microfibrillated cellulose (MFC) 104, embedded into thepores of a low-density nonwoven substrate 106 and a high density layer108 of the nonwoven substrate 106. The superabsorbent content ispreferably from 70-95%. A process of manufacturing the absorbent core100 has been developed by the Japan Absorbent Technology Institute(JATI) and available under the trade name MEGATHIN. The details of themanufacturing process and other characteristics of the MEGATHIN sheetare described in U.S. Pat. No. 6,790,798, hereby incorporated byreference.

The absorbent core 100 may include one or more layers or strata ofnatural or synthetic fibers. Superabsorbent polymers (SAP) may beincorporated into the absorbent layer as particles, granules, flakes,etc., and may be included as a discrete stratum or mixed with theaforementioned fibers. SAP particles of various type, size or shapesuitable for use in an absorbent core may be employed in embodiments ofthe invention. Materials such as fillers, perfumes, surfactants, andadditives may be included in the absorbent composite. In a preferredembodiment, the absorbent composite contains 50-97% by weight of SAP and3-50% by weight of fibers. More preferred embodiments of the presentinvention include polyacrylate-based SAPs and resilient fibers such aspolyester (PET), polyolefin (PP or PE), or nylon fibers (Hydrofil™).

Basis weights of the absorbent composite can be adjusted and optimizedfor particular purposes over a wide range. Furthermore, multiple layersof the absorbent composite can be assembled to achieve the desired totalbasis weight. Generally, the basis weight of a single absorbentcomposite layer can range, for example, from about 50 grams per squaremeter (gsm) to about 1000 gsm, and more specifically from about 100 to500 gsm.

In preferred embodiments of the present invention, the absorbent core100 (or layer portions thereof) is slit according to a predeterminedpattern to increase fluid intake rate and flexibility. The absorbentcore 100 may include multiple layers, with slit patterns being differentbetween layers. In one embodiment, core 100 includes two or more layers,with at least one layer having a slit pattern and another layer havingsubstantially no slits.

FIG. 2A and FIG. 2B are top plan views of an absorbent core 100 with amultiplicity of short slits 10 arranged in various patterns along themachine direction (MD) and cross direction (CD). As noted previously,the number and length of the slits can be varied to deliver the intakeperformance and flexibility required. In this embodiment, a slit levelof at least 0.1 cm⁻¹ and a slit length of at least 0.2 cm is required.

Another exemplary embodiment is shown in FIG. 3. The particulararrangement of the three slits, two long side slits 20 and center slit30 encourages the folding of the absorbent core to form of an absorbentbucket that effectively reduces early leakage.

FIG. 4 is another embodiment of the present invention with long centerslit 30 and side slits 20, together with a multiplicity of smaller slits10 placed between the long slits 20 and 30, to achieve higher liquidintake rates in addition to preferentially bucket formation.

FIG. 5 is a top plan view of absorbent core 100 with patterned slits 40at ends and sides in addition to long side slits 20. Slits patternedtowards the ends of the product provide faster intake rates in thoseregions and hence reduce waist leakage. Absorbent core 100 constructionmay also include more than one absorbent composite layer. For example, atwo-layer absorbent core structure can be assembled wherein the toplayer 100 is slit 20 for enhanced intake and the bottom absorbent 200remains unslit. FIG. 6 is a cross sectional view taken along thetransverse direction view of such a layered absorbent core structure. Anexample of the present invention may include a liquid pervious top sheetor an acquisition layer or both.

FIG. 7 is a cross sectional view taken along the longitudinal directionof an absorbent article such as a diaper of a two-layer absorbent corestructure described by FIG. 6 and depicting the placement of theinventive slit structure centrally around the crotch area only.

FIG. 8 illustrates the use of appropriately disposed slits 20 to providebend areas that enable the absorbent article to follow the bodycurvature for improved fit and appearance.

In another embodiment illustrated by FIG. 9, appropriately placed slitsin the absorbent core 100 provide cut 40 and bend/fold lines 50 andyield a hourglass shaped absorbent composite from a rectangularabsorbent composite. Similarly FIG. 10 depicts an hourglass shapedabsorbent composite created by slitting and folding along slit lines 20.

Exemplary embodiments of the present invention were subjected toexperimentation. Descriptions of the test procedures follows.

Intake Rate—Intake rate is determined using the liquid strikethroughtest. The test determines the time required for an absorbent compositeto intake a preset amount of liquid. A reduction in liquid strikethroughtime indicates an improvement in intake rate. The liquid strike throughtime is measured using the known Fluid Intake Flowback Evaluation(FIFE)-type test apparatus. In a typical experiment, three consecutive40 ml quantities of test liquid (e.g., 0.9% saline solution) are appliedto the absorbent core sample at 15 minute intervals and the respectivestrikethrough times are recorded.

Flexibility—Flexibility is determined using the drape stiffness test.This test determines the bending length of a material subject tocantilever bending without application of external forces. What ismeasured is the drape stiffness or resistance to bending of thematerial. Bending length is a measure of the interaction betweenmaterial weight and material stiffness as shown by the way in which afabric or a sheet bends under its own weight. This is a reflection ofthe stiffness of a planar material when bent in one plane under theforce of gravity.

For example, a 10 cm×5 cm specimen was slid, in a direction parallel toits long dimension, so that its leading edge projected from the edge ofa horizontal surface. At predetermined lengths of specimen pushed pastthe leading edge of the horizontal surface, the vertical distancebetween the horizontal surface and the tip of the bent specimen wasmeasured. This vertical distance is commonly referred to as thematerial's bending length or flexibility. The greater the bendinglength, the easier the material is to bend. Thus higher bending lengthsindicate a more flexible material. Materials can be tested forflexibility along the MD or cross direction (CD).

EXAMPLES

Column 1 of Table 1 provides the absorbent composites used in theaccompanying examples in accordance with the present invention. Thesecomposites had a very high superabsorbent content, are thin and have ahigh composite density. The corresponding bulk density, calculated asthe reciprocal of composite density is low, indicative of the thinnessof the composite. The superabsorbent used was a polyacrylate-based SAPwith a centrifuge retention capacity (CRC) of about 36 g/g, a free swellcapacity of about 53 g/g, and an average particle diameter of 200-300microns.

TABLE 1 SAP Fiber % Total Super- basis components SAP absorbent Thick-Bulk absorbent wt, Fiber basis wt, in basis wt, ness, Density Density,(SAP) gsm components gsm composite gsm cm g/cc cc/g 1 Nippon 125 92%PET, 30 80.65% 155 0.03 0.52 1.94 Shokubai  8% MFC 2 Nippon 250 92% PET,95 72.46% 345 0.075 0.46 2.17 Shokubai  8% MFC

TABLE 2 CD Slit Flex- Strikethrough Top Level ibility, Bottom time (s)Absorbent Layer cm⁻¹ cm Layer 1 2 3 Top and bottom slit 1.66 2.32 notslit 18.1  34.45 39.8  layers: 125 gsm MEGATHIN ™, 80% SAP, 20% fiber,mechanically softened Top and bottom not 0 1.66 not slit 33.55 38.7540.25 layers: 125 slit gsm MEGATHIN ™, 80% SAP, 20% fiber, mechanicallysoftened Effect of slitting 46.05% 11.10% 1.12% top layer: % improvementin strikethrough time

The effect of slitting the absorbent core on intake rate and flexibilityis shown in Table 2. Two layers of the absorbent composite were used. Inthis dual layer absorbent core construction, only the top absorbentlayer was slit. A slit length of 1.2 cm and a slit pattern similar tothe pattern in FIG. 2 was used. The slits were oriented in the machinedirection (MD), staggered, spaced 0.6 cm apart in the MD and spaced 0.8cm in the cross direction (CD). The slit level for this slit pattern was1.66 cm⁻¹. The absorbent composites were also mechanically pre-softenedby passing the composites through an embossing unit with intermeshedgears. The CD bending length at a 4 cm overhang (i.e., 4 cm of theinventive absorbent composite along its CD direction was projected pastthe edge of the horizontal surface) was measured and reported as thecomposite flexibility.

It is readily seen that the absorbent composite subjected to slittingaccording to the present invention had a significantly improved intakerate and flexibility.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims. Moreover, thescope of the present application is not intended to be limited to theparticular embodiments of the process, machine, manufacture, compositionof matter, means, methods and steps described in the specification. Asone of ordinary skill in the art will readily appreciate from thedisclosure of the present invention, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the present invention.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps.

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 36. A method of manufacturing a disposableabsorbent article comprising: selectively defining one or more regionsof greater liquid uptake upon an absorbent core having superabsorbentmaterial; and slitting the absorbent core to provide a plurality ofslits, with a greater number of slits per unit area defining a region ofgreater liquid intake as compared to another region having a fewernumber of slits per unit area.
 37. The method of claim 36, wherein saidone ore more regions of greater liquid intake are defined in a mannerdependent upon an end use of the absorbent article.
 38. The method ofclaim 36, wherein said slitting defines a patterned region of increasedflexibility as compared to another less-flexible region.
 39. Anabsorbent article, the absorbent article comprising: a liquid imperviousback sheet; and an absorbent core containing at least one layer ofsuperabsorbent material (SAP) and including a plurality of slits, saidplurality of slits extending through at least a portion of saidsuperabsorbent material; and wherein said plurality of slits have a slitwidth of between 1 micron and 1000 microns.
 40. The absorbent article ofclaim 39 wherein at least some of the plurality of slits are partialslits that extend from a top surface of the absorbent core towards theback sheet but do not penetrate the bottom surface.
 41. The absorbentarticle of claim 39 wherein said plurality of slits are disposed tofacilitate greater liquid intake of said absorbent core as compared toan identical, but non-slitted, core, and further facilitate improvedflexibility of the absorbent core in a predetermined direction and tosupport a capillary flow of liquid into an interior of the absorbentcore.
 42. The absorbent article of claim 39 wherein the absorbent coreincludes from 50% to 97% by weight of superabsorbent material and from3% to 50% by weight of fibers (104), and a low density nonwovensubstrate and a high density nonwoven substrate, the superabsorbentparticles being intermixed with microfibrillated cellulose and embeddedinto the pores of a low density nonwoven substrate and a high densitylayer of the nonwoven substrate.
 43. The absorbent article of claim 39wherein said plurality of slits have a slit level that is greater than0.1 cm⁻¹.
 44. The absorbent article of claim 39 wherein said absorbentcore has a basis weight from 50 grams per square meter (gsm) to 1000gsm, and a low density nonwoven substrate and a high density nonwovensubstrate, the superabsorbent particles being covered or intermixed withmicrofibrillated cellulose and embedded into the pores of a low densitynonwoven substrate and a high density layer of the nonwoven substrate.45. The absorbent article of claim 44 wherein said absorbent core has abasis weight from 100 gsm to 500 gsm.
 46. The absorbent article of claim39 wherein the absorbent core is folded along at least one region ofmaterial discontinuity.
 47. The absorbent article of claim 39 whereinthe absorbent core is subjected to a mechanical softening process. 48.The absorbent article of claim 39 wherein the absorbent core is foldedalong two or more lines of material discontinuity, wherein said two ormore lines are oriented in a product longitudinal direction and locatedabout a central region of the absorbent article, thereby defining anhourglass shape.
 49. The absorbent article of claim 39 wherein theabsorbent core further comprises a second layer of SAP material havingsubstantially fewer slits as compared to the first SAP layer and whereinsaid slits of said first layer include cross direction slits.
 50. Theabsorbent article of claim 39 said absorbent core has a basis weightfrom 50 grams per square meter (gsm) to 1000 gsm, and a low densitynonwoven substrate and a high density nonwoven substrate, thesuperabsorbent particles being covered or intermixed withmicrofibrillated cellulose and embedded into the pores of the lowdensity nonwoven substrate and the high density layer of the nonwovensubstrate.
 51. The absorbent article of claim 49 wherein the absorbentcore includes at least two SAP layers disposed one on top of another,and wherein the top layer has slits in the machine direction and slitsin the cross direction.
 52. The absorbent article of claim 51 whereinthe layer below the top layer is not modified with slits and whereineach said layer of said absorbent core has a basis weight from 50 gramsper square meter (gsm) to 1000 gsm, and a low density nonwoven substrateand a high density nonwoven substrate, the superabsorbent particlesbeing covered or intermixed with microfibrillated cellulose and embeddedinto the pores of the low density nonwoven substrate and the highdensity layer of the nonwoven substrate.
 53. The absorbent article ofclaim 1, wherein said slits are disposed on the at least one layer ofsuperabsorbent material, and wherein the absorbent core comprises fromabout 61% to about 97% by weight of a superabsorbent material, fromabout 3% to about 39% by weight of non-absorbent nonwoven resilientfibers, and 0% by weight of absorbent hydrophilic fibers, wherein thesuperabsorbent material comprises particles and the non-absorbentnonwoven resilient fibers form a low-density layer and a high-densitylayer.
 54. A method of manufacturing a disposable absorbent articlehaving a crotch area, the method comprising: providing a generallyliquid impervious back sheet; connecting an absorbent core to said backsheet, said core including at least one layer containing superabsorbentmaterial and wherein the absorbent core includes from 50% to 97% byweight of superabsorbent material and from 3% to 50% by weight offibers, and a low density nonwoven substrate and a high density nonwovensubstrate, the superabsorbent particles being covered or intermixed withmicrofibrillated cellulose and embedded into the pores of a low densitynonwoven substrate and a high density layer of the nonwoven substrate;and slitting said at least one layer of said absorbent core in saidcrotch area, said slitting improving the liquid intake and flexibilityof the absorbent core as compared to a similar, but non-slitted, core,wherein said plurality of slits have a slit width of between 1 micronand 1000 microns to support a capillary flow of liquid into an interiorof the absorbent core.